This exploratory study is designed to ensure the safety of HIV-infected volunteers who complete research protocols that include an analytic treatment interruption (ATI). This is a prospective cohort study of volunteers who were diagnosed with HIV during early acute HIV infection, treated with antiretroviral therapy (ART) and subsequently enrolled in a clinical study that included ATI. After completion of study participation that involves ATI, participants will be recruited into this study for continued clinical and laboratory monitoring.